1. Field of the Invention
This invention relates to a press device which is used for shaping or closed die forging of a blank material such as a steel plate.
2. Description of the Related Art
A press device for shaping a blank material such as a steel plate by press work is already known wherein a press force generating means and a shaping element means are disposed in a vertically opposing relationship within a press frame provided for receiving a press thrust thereon and which includes a guide means for guiding a cross head for sliding movement in the direction of an axis of the press.
Such device will be described in outline with reference to FIGS. 13 to 15. The press device shown in FIGS. 13 to 15 includes a press frame 1 which is shown as of the wire winding type wherein a piano wire 2 is wound around an outer periphery of the press frame 1. The device further includes an upper pressure receiving plate 3 and a lower pressure receiving plate 4 secured in a vertically opposing relationship to each other within the press frame 1.
The press device further includes a press force generating means 5 which is composed of a lid member 6 secured to the upper pressure receiving plate 3, a cylinder 7 in which the lid member 6 is fitted, and a main ram or piston 8 also fitted in the cylinder 7. The main ram 8 has an outer circumferential flange 9 at an intermediate portion in an axial direction thereof and is fitted also in a cylindrical portion 11 of a cross head 10 below the cylinder 7.
The press device further includes a shaping element means 12 including a die member 14 mounted on the lower pressure receiving plate 4 and having a shaping portion 13 thereon. The shaping element means 12 has a plurality of knockout means 15 built therein.
The press device further includes a blank holder 16 mounted on the lower face of the cross head 10 for pressing against a blank material 17 on the die member 14.
The press device further includes four blank holder actuating cylinder devices 18, four balance cylinder devices 19, a pair of cross head lifting cylinder devices 20, and a pair of cross head guide means 21.
In the conventional press device, a blank material 17 on the die member 14 is shaped into a predetermined shape by operating the blank holder actuating cylinder devices 18 to move down the cross head 10 and the blank holder 16 to press against an outer peripheral portion of the blank material 17 and then causing an oil pressure (hydraulic pressure) to act in the cylinder 7 to move down the main ram 8 until a lower end portion of the main ram 8 is advanced into the shaping portion 13 of the die member 14.
After such shaping, the main ram 8 is moved up by the balance cylinder devices 19 and then the cross head 10 is moved up by the lifting cylinder devices 20 therefor.
FIG. 16 shows a press device for shaping a blank material into a shape which has an inclined face at a recessed portion thereof. Referring to FIG. 16, each of a main ram 8A and a shaping portion 13A has an inclined face thereon.
The conventional press device shown in FIGS. 13 to 15 has a problem that it is comparatively great in overall height and hence in overall size because the cross head 10 is disposed in a vertically opposing relationship below the cylinder 7 of the press force generating means 5.
Such great overall size of the press device gives rise to complication of the cross head guide means 21, increase in overall size of an exchanging means of a seal member for the main ram 8, increase in number of parts, deterioration in handling facility and so forth.
Further, since the press thrust is technically carried on the press frame 1, disposition of the cylinder 7 and the cross head 10 in a vertically opposing relationship within the press frame 1 will allow a comparatively great amount of deformation of the press frame 1, which gives rise to a disadvantage that the press frame 1 must be made very rigid and strong or else the press force must be excessively small. Such disadvantages must be eliminated whether the press frame 1 is of the column type, the wire winding type or any other type, but they are a serious problem particularly in a press device of the wire winding type because it is deformed upon winding of a wire or upon application of a load (upon shaping operation).
On the other hand, the case of the press device shown in FIG. 16 wherein the main ram 8A and the shaping portion 13A have inclined face portions thereon, an eccentric load is produced during shaping, which will give rise to a bending moment. A lateral load caused by such bending moment is received by the cross head guide means 21 having a gate-like configuration. However, since a pair of supporting portions 21A and 21B of the guide means 21 are vertically spaced by a comparatively great distance from each other, a guide rod 21C of the guide means 21 must necessarily have a large diameter. Or otherwise, there is a possibility that the guide rod 21C of the guide means 21 may be put into a non-usable condition particularly with a wire winding press frame which is comparatively low in rigidity against a load acting in a lateral direction.